Interactive display devices such as touch screen displays and touch panel devices are commonly implemented with computing devices such as portable computers, cell phones, personal digital assistants (PDAs), and other hand held portable computing devices, to allow user interaction with the device or applications executed on the device using a display screen. A user can interact with the device or application by contacting a touch sensitive surface overlaying a display screen in predetermined regions (using a pointing device such as a stylus or other contact means such as finger contact) so as to select graphical objects displayed on a screen or input text, etc.
FIG. 1 schematically illustrates a computing device (10) having an interactive display device (100) with a conventional framework. The interactive display device (100) comprises a display unit (110) and a touch panel (120) (or digitizer) mounted on the front-side surface of a housing (130) of the computing device (10) with the digitizer (120) stacked as an overlay on the display unit (110). The digitizer (120) is a contact sensitive layer that can be designed using one or various known techniques and structures to detect motion, touch, position, etc. of an object such as a stylus, pen, pointing device, a human's finger, etc, in contact with the surface of the digitizer (120) and generate signals that causes a graphic cursor to be moved on the screen of the display unit (120). The display unit (110) may be a liquid crystal display (LCD), for example. Interactive touch screen display devices are used with graphical user interfaces so as to present users with depictions of controls and text that can be manipulated by user operated pointing devices to provide what is referred to as a “direct manipulation” user interface, as is known in the art. In order to support a “direct manipulation” user interface, the interactive display device (100) having a stacked, overlay framework as depicted in FIG. 1 must meet certain design criteria.
For instance, the digitizer (120) must be designed having a contact sensitive surface with a footprint that is at least the same size as (and aligned to) the footprint of the display screen of the display unit (110). The digitizer (120) must be constructed using transparent glass or rigid plastic materials so that displayed graphics, objects, etc. can be seen through the overlying digitizer (120). Moreover, to implement a “direct manipulation” user interface using the conventional interactive display device (100) of FIG. 1, the physical or synthetic resolution of the digitizer (120) must be sufficient (110) so that the position of the user contact on the overlying digitizer (120) relative to the position on the display screen (110) directly under the contact point can be determined with sufficient precision. Indeed, for finger contact designs, it is important to provide sufficient resolution that allows the user to accurately position a graphical cursor or otherwise select/active a graphical object or menu option displayed on the screen just below the user contact point. This precision detection is important for effective user operation for direct manipulation user interfaces where users expect to be able to interact with graphical objects, etc., directly below the point underlying the user's perceived contact point.
There are limitations and disadvantages associated with conventional interactive display devices having stacked frameworks, such as depicted in FIG. 1. For instance, the use of high resolution digitizers as required for direct manipulation user interactive display systems can be extremely costly in terms of manufacturing costs, as well as the complex system integration of hardware and software required for high-resolution digitizers. Furthermore, with a stacked interactive display framework of FIG. 1, the display unit (110) can be damaged as a result of repeated contact pressures that are generated when operating the touch screen overlay (120) with a stylus or fingertip, which can lead to a shortened lifespan of the display.
Furthermore, as portable computing devices are made increasing smaller with smaller screen sizes and more compact graphic user interfaces, interactive display devices with stacked frameworks as depicted in FIG. 1 pose practical limitations with regard to scaling screen size and user interface graphic content. Indeed, when a touch screen overlay is used, a user's fingers and/or a stylus will obscure part of the display as the user's finger or stylus is manipulated to make contact at a desired position. In this regard, it can be difficult for a user to make a selection of a target object on a small display screen having a densely packed graphical interface using fingertip contact, as the user's fingertip may cover more than a single control or selection. As such, graphic user interfaces must be designed to present relatively large interactive targets to accommodate the relatively large contact footprint of a user's finger and otherwise compensate for relative imprecision of the human finger as an input mode.